Haruhiko Nakata

Persistent organochlorine residues and their accumulation kinetics in Baikal seal (Phoca sibirica) from Lake Baikal, Russia.

Organochlorine compounds (OCs) such as DDTs (DDT and its metabolites), PCBs (polychlorinated biphenyls), CHLs (chlordane compounds), and HCHs (hexachlorocyclohexanes) were determined in the blubber of Baikal seal (Phoca sibirica) and their fish diet collected from Lake Baikal in 1992. Residue levels of DDTs and PCBs were in the ranges of 4.9-160 μg/g and 3.5-64 μg/g on a lipid weight basis, respectively. The concentrations of CHLs and HCHs were approximately 1 or 3 orders of magnitude lower than those of DDTs and PCBs. Comparison of OC residue levels with those reported for other pinnipeds suggests that Baikal seal is highly contaminated species vulnerable to OC toxicity. A positive age-dependent accumulation of DDTs, PCBs, and CHLs was found in males, while a steady state observed in females suggested the transfer of these chemicals from mother to pup through gestation and lactation. On the basis of contaminant burdens in adult seals, it was estimated that an adult female Baikal seal transfers about 20% of its total DDTs and 14% of its total PCBs to the pup during a reproductive process. Based on the data from isomer-specific analysis of PCBs, it can be suggested that Baikal seals have a higher or comparable capacity to metabolize toxic contaminants than marine mammals, but it is apparently lower than terrestrial mammals, which seems to be a causative factor for the higher accumulation of OC residues in this species.

Accumulation pattern of organochlorine pesticides and polychlorinated biphenyls in southern sea otters (Enhydra lutris nereis) found stranded along coastal California, USA

Concentrations of PCBs, DDTs (p,p-DDE, p,p-DDD and p,p-DDT), HCHs (α-, β-, γ-isomers), chlordanes (trans-chlordane, cis-chlordane, trans-nonachlor, cis-nonachlor and oxychlordane) and HCB (hexachlorobenzene were measured in liver, kidney and brain tissues of adult southern sea otters (Enhydra lutris nereis) found stranded along coastal California, USA, during 1992–96. The contamination pattern of organochlorines in sea otters from several locations was in the order of DDTs>PCBs>>CHLs>HCHs>>HCB, whereas those from Monterey Harbor contained greater concentrations of PCBs than of DDTs. Hepatic concentrations of PCBs and DDTs were in the ranges of 58–8700 and 280–5900 ng/g, wet weight, respectively, which varied depending on the geographic location. Sea otters collected from Monterey Harbor contained the greatest concentrations of PCBs and DDTs. In general, accumulation of DDTs, CHLs and PCBs was greater in kidney than in liver, whereas that of HCHs was similar in both the tissues. The gender difference in organochlorine concentrations was less than those reported in cetaceans. The composition of DDTs, HCHs and CHLs compounds in sea otter tissues indicated no recent inputs of these compounds in coastal California. Sea otters that died from infectious diseases, neoplasia and emaciation contained higher concentrations of DDTs than those that died from trauma.

Contamination by persistent organochlorines in small cetaceans from Hong Kong coastal waters

Abstract Blubber samples of 2 cetacean species, the Indo-Pacific hump-backed dolphin ( Sousa chinensis ) ( n =11) and finless porpoise ( Neophocaena phocaenoides ) ( n =9), collected from Hong Kong coastal waters were analysed for persistent organochlorines. Mean concentration in the blubber of DDTs was ranked first (46 μg/g wet wt.), followed by PCBs (24 μg/g wet wt.), HCHs (0.76 μg/g wet wt.), chlordane compounds (0.38 μg/g wet wt.) and HCB (0.07 μg/g wet wt.). The present cetacean species may potentially be faced with high risk due to the elevated level of DDTs and PCBs. Relatively high concentrations of PCBs and DDTs can be attributed to the continuous environmental input of these compounds in the Far East region including Hong Kong. Highly chlorinated PCBs such as IUPAC Nos. 138, 153, 180 were the prominent congeners, accounting for 39% of the total PCBs. Mean concentrations of 6 non- and mono- ortho coplanar congeners were 2.1 and 2.8 μg/g wet wt. in the hump-backed dolphin and finless porpoise, respectively. Among highly toxic coplanar PCBs, mono- ortho congener IUPAC No. 118 and non- ortho congener IUPAC No. 126 were estimated to have the greatest toxicity contribution. Tris (4-chlorophenyl) methane (TCPMe) and tris (4-chlorophenyl) methanol (TCPMeOH), which have been the most recently identified microcontaminants, were also detected with the highest concentration of 290 and 300 ng/g (wet wt. basis), respectively. The concentrations of TCPMe relative to TCPMeOH in cetaceans from Hong Kong coastal waters were significantly higher than those found in various seals collected from other parts of the world, suggesting the different metabolic system of these two compounds between seals and cetaceans. Correlations between the concentrations of tris -chlorophenyl compounds with other persistent organochlorines such as HCHs, CHLs, DDTs and PCBs were significant, suggesting their accumulation nature similar to these organochlorines.

Persistent organochlorine residues in marine and freshwater fish in Cambodia

Abstract Concentrations of persistent organochlorines (OCs) such as PCBs (polychlorinated biphenyls), DDT compounds (DDTs), HCH (hexachlorocyclohexanes) isomers (HCHs), chlordane compounds (CHLs) and HCB (hexachlorobenzene) were determined in 27 species of marine and freshwater fish collected from Cambodia. DDT and its derivatives were the predominantly detected compounds in both marine and freshwater fish. PCBs were the second highest followed by HCHs, CHLs and HCB. Freshwater fish contained higher concentrations of DDTs than those of marine fish, implying that the sources of DDTs originate from inland watersheds such as the Mekong River, Basac River, Tonlesap River and Tonlesap Great Lake. Comparison of the OCs residue levels in Cambodian fish with those in other Asian and Oceanic regions suggested that Cambodia is one of the less-contaminated countries by OCs. In other words, it can be concluded that Cambodia has kept “Clean Environment” among Asian and Oceanic countries.

Bioaccumulation profiles of polychlorinated biphenyls including coplanar congeners and possible toxicological implications in Baikal seal (Phoca sibirica).

Isomer specific concentrations of individual polychlorinated biphenyls (PCBs) including toxic non-ortho (IUPAC 77, 126, 169), mono-ortho (105, 118, 156) and di-ortho (137, 138, 153, 180) coplanar congeners were determined in the blubber of 40 Baikal seals (Phoca sibirica) and as their fish diet collected from Lake Baikal, Siberia. Residue levels of total PCBs in Baikal seals were noticeably high and comparable to those reported for seals from the North Sea, suggesting the recent usage of this compound in the watershed of Lake Baikal. Non-, mono-, and di-ortho coplanar congeners were also detected in Baikal seals and fish. An approach to estimate bioaccumulation profiles of PCB congeners revealed that the non-ortho PCBs, IUPAC 77, 126 and 169 seemed to be less persistent than other congeners. Furthermore, selective biotransformation of PCB congeners having either meta-para vicinal H atoms or both adjacent chlorinated meta-para and ortho-meta positions has been suggested. Comparison of 2,3,7,8-TCDD toxic equivalents (TEQ) of non-, mono- and di-ortho coplanar congeners in Baikal seals with those for other marine mammals suggested higher enrichment of mono-ortho congeners, particularly IUPAC 105 and 118, which contributed significantly to the total TEQs in Baikal seals. Results imply that the TCDD-like toxicity is relatively serious in Baikal seals, because of the enrichment of these toxic PCB congeners in tissues.

In vitro inhibition of hepatic cytochrome P450 and enzyme activity by butyltin compounds in marine mammals

The present study attempted to examine the in-vitro inhibition of hepatic microsomal P450 content and activity by butyltins in marine mammals and discussed on their possible effects in animals in the wild. Decreases in P450 content and the activities of ethoxyresorufin O-deethylase (EROD, catalyzed by CYPIA subfamily) and penthoxyresorufin O-depentylase (PROD, catalyzed by CYP2B subfamily) by tributyltin (TBT) were observed in in-vitro experiments using hepatic microsomes of a pinniped and a cetacean. Among P450 family, EROD activity is more sensitive to TBT than P450 content and PROD activity, indicating a specific mode of action of TBT on different P450 forms. On the other hand, dibutyltin and monobutyltin have no inhibitory effect on EROD activity at concentrations less than 0.5 mM, indicating that the inhibition of enzyme activity in hepatic microsome of marine mammal is mainly by TBT. TBT concentrations that affect P450 contents and activities are above 10 times higher than the values found in the liver of various marine mammals.

Seroepidemiological survey of distemper virus infection in the Caspian Sea and in Lake Baikal

Forty Caspian seals were surveyed seroepidemiologically between 1993 and 1998 around the times of mass mortality that occurred in 1997 in the Caspian Sea and seven Baikal seals were also surveyed in 1998. Virus neutralizing tests and ELISA clearly suggested that distemper virus epidemic was caused in Caspian seals before the spring of 1997 and that CDV infection continued to occur in Lake Baikal in recent years.

Contamination of the ecosystems of lake baikal by persistent organochlorines

Publisher Summary This chapter presents a study that investigates the contamination of Lake Baikal by persistent organochlorines (OCs), including oolychlorinated biphenyls (PCBs), DDTs, HCHs, and chlordanes, by assessing in air, water, sediment, soil, fish, and seal samples collected from Lake Baikal. According to the findings of the study, DDT concentrations in air and water are one order of magnitude higher than in the Arctic. HCH and PCB concentrations in water samples are found to be higher in the lower reaches of the Selenga River and the southern basin of the lake, suggesting the presence of local sources of these contaminants. Higher concentrations of PCBs and DDTs are found in the blubber of Baikal seals. A positive age-accumulation of PCBs, DDTs, and CHLs is found in males, whereas a steady state is observed in females, implying the transfer of these chemicals from mothers to their pups. Isomer-specific analysis of PCBs suggests that Baikal seals have higher or comparable capacity to metabolize toxic contaminants than marine mammals, but a clearly lower capacity than terrestrial mammals, which seems to be a causative factor in the higher accumulation of OCs in this species.